1. Field of the Invention
This invention relates to a method for dynamically tuning seismic transducers to a specified resonant frequency.
2. Description of the Prior Art
One type of motion-sensing transducers utilizes a spring-suspended, moving coil assembly wherein the spring and coil assembly oscillate at a desired resonant frequency. In order to maintain consistent transient response among many such transducers, commercial standards require that the actual resonant frequency of each transducer must fall within .+-.5% of the desired resonant frequency, particularly for digital grade geophones used in geophysical exploration.
Under conventional manufacturing techniques, springs and coil assemblies are mass produced. However, due to limitations inherent in the production process, the springs and coil assemblies cannot be manufactured so perfectly that a randomly-chosen spring can be combined with a randomly-selected coil assembly to produce a transducer with a resonant frequency within the commercially acceptable tolerance range. The springs and coil assemblies must therefore be sorted to match a spring that is out of tolerance in one direction with a coil assembly that is out of tolerance in another direction so that the combination of the two produces a transducer with the desired resonant frequency. The procedure of selective matching of springs and coil assemblies is necessarily a hand operation that is time consuming and costly. Additionally, there is an inherent limit to the degree of spring and coil assembly mismatch that can be tolerated.